Ball seats that allow the ball to land and seat to operate a tool with built up pressure against the seated ball and thereafter pass the ball or object past the seat have been used in the past. One example uses a tapering member with a central lower opening that is backed by segments that support the tapered member. The tapered member without the segments supporting it from below would not be strong enough to retain a seated ball at the needed pressure differential across the ball. When the ball is on the seat the pressure is built up to a first level and a tool is operated. After the tool is operated pressure is further raised so that the ball seat assembly breaks a shear pin and moves axially in a manner that allows the dog supports to retract so that pressure on the seated ball extrudes the opening in the seat to the point that the ball can pass. One such system is illustrated in U.S. Pat. No. 6,634,428. The problem with this system is that the seat opening does not extend uniformly as the ball is blown clear so that later when the well is brought in the ball rises to the seat but can still get hung up on the now enlarged but potentially severely misshapen ball seat opening.
Other examples of known designs can be seen in U.S. Pat. Nos. 6,155,350; 7,464,764; 7,469,744; 7,503,392; 7,628,210; 7,637,323 and 7,644,772.
What is needed and provided by the present invention is a ball seat that is made by the retractable segments so that when an object lands on them there is still some leakage in the gaps between the segments but its extent is controlled so that the tool can still be operated with an elevated pressure. Then with an even higher pressure the seat assembly moves axially to let the segments retract and the ball to pass. Also used above the segments is a tapered member with a bottom opening that is larger than the object so that when the object falls the taper guides the object through the opening and onto the supported segments. When the segments translate axially so that they can retract radially the tapered member is not extruded as its original lower end opening was initially larger than the object. Thus, when the well is later brought in from below a series of such assemblies, the ball can be redelivered to the surface without hanging up on ball seats that are so distorted from ball extrusion that they do not permit the ball or object to pass back up the string to the surface. In the preferred system there are a series of such assemblies attached to sliding sleeves to open a zone to be produced to fracturing fluid delivered under pressure. A single ball can open multiple valves and seat below them all to allow pressure buildup in the zone of interest before allowing the ball to be recovered to the surface. Those skilled in the art will better understand the invention from the detailed description of the preferred embodiment and the associated drawings while understanding that the full scope of the invention is to be found in the appended claims.